Ultraviolet ray-absorbing, colorless and transparent soda-lime-silica glass

ABSTRACT

An ultraviolet ray-absorbing, colorless and transparent soda-lime-silica glass is disclosed, which glass is prepared by irradiating a cerium containing soda-lime-silica glass with light having wavelengths in far- to near-ultraviolet region and thereby reducing transmittance to light with wavelengths in the region of 300-400 nm.

TECHNICAL FIELD

[0001] The present invention relates to an ultraviolet ray-absorbing,colorless and transparent soda-lime-silica glass, and to glass bottlesmade of the glass. In further detail, the present invention relates toan ultraviolet ray-absorbing, colorless and transparent soda-lime-silicaglass, and to glass bottles made of the glass, which is free of greenishor bluish tint, yet which can prevent their contents from undergoingultraviolet ray-induced coloration, discoloration, fading in color ordeterioration of the flavor and, inter alia, prevent coloration ofrefined “sake”, coloration or fading in color of wines, anddeterioration of the flavor of refined “sake” and wines.

BACKGROUND ART

[0002] Amber, green or blue bottles have been widely used for refined“sake” or for beer in order to prevent light-induced coloration,discoloration, fading in color or deterioration of the flavor of theircontent beverages. Those bottles are all deeply colored and thus preventtheir contents from being seen as they are through the bottles. Thus,there have been needs for transparent, colorless, high-brightness glassbottles which thereby allow their contents to be seen more clearly.

[0003] In many cases, however, transparent, colorless, high-brightnessglass has, at the same time, high transmittance to ultraviolet ray.Ultraviolet ray passing through a glass bottle is apt to inducecoloration, discoloration or fading in color of its contents. In thecase, inter alia, where refined “sake” is its content, yellowing in itscolor would entail deterioration of its flavor, thereby greatlyimpairing its commercial value. In the case of wines, too, there areproblems that they would undergo coloration, fading in color anddeterioration of the flavor.

[0004] As a means to solve these problems, Japanese Patent ApplicationPublication No. S52-47812 discloses an ultraviolet ray-absorbing,colorless soda-lime glass which contains CeO₂ and V₂O₅ as ultravioletray absorbents, and MnO₂ or Se and, as needed, Co₃O₄ as decolorizingagents. This glass, however, has a substantial risk of undergoingcoloration as a result of solarization because of coexisting CeO₂ andV₂O₅. Japanese Patent No. 2528579 and Japanese Patent ApplicationPublication No. H8-506314 disclose ultraviolet and infraredrays-absorbing glasses containing Fe₂O₃, FeO, CeO₂ and manganese oxide.However, due to their high total iron content together with theirconsiderable content of FeO, these glasses cannot be free of a green toblue color. This renders those glasses unsatisfactory for use in theproduction of colorless and transparent, high-brightness bottles thatallow their contents to be seen more clearly.

[0005] Thus, there have been needs for colorless and transparent,ultraviolet ray-absorbing glass bottles which, while allowing theircontents to be seen more clearly on store shelves as a result of theirhigh transmittance to light in the visible region, enable to keep theircontents from exposure to ultraviolet ray in the process of distributionand on store shelves.

[0006] In order to meat the needs, the present inventors previouslyfound that an ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass that is highly absorptive of ultraviolet raywhile having high transmittance to visible light, is obtained by addingpredetermined proportions of SO₃, cerium oxide, Fe₂O₃, FeO, manganeseoxide and, as needed, cobalt oxide to a conventional basic compositionof soda-lime-silica glass, and filed on the basis of the findings aninternational application PCT/JP99/04564 (WO 00/12441). However, thereare still needs for glass bottles that allow for further reduction intransmittance to ultraviolet ray, while remaining colorless andtransparent.

[0007] The objective of the present invention is to provide anultraviolet ray-absorbing, colorless and transparent soda-lime-silicaglass and glass bottles made thereof which, while maintaining hightransmittance to light in the visible region and thereby allowing theircontents to be seen more clearly, absorb more ultraviolet ray andthereby serve to prevent ultraviolet ray-induced coloration,discoloration, fading in color or deterioration of the flavor of theircontents.

DISCLOSURE OF INVENTION

[0008] As a result of studies directed to the above objective, thepresent inventors found that irradiation of a cerium-containingsoda-lime-silica glass with light having wavelengths in the far- tonear-ultraviolet region gives rise to a glass with reduced transmittanceto ultraviolet ray, without affecting the spectral characteristics ofthe glass in the visible region. The present invention was accomplishedbased on this finding.

[0009] Thus, the present invention provides an ultravioletray-absorbing, colorless and transparent soda-lime-silica glass that isobtained by irradiating a cerium-containing soda-lime-silica glass withlight having wavelengths in the far- to near-ultraviolet region, therebycausing reduction in transmittance to light with wavelengths in theregion of 300-400 nm.

[0010] Herein, the phrase “reduction in transmittance to light withwavelengths in the region of 300-400 nm” means general reduction intransmittance to light with wavelengths in the region of 300-400 nm andit is allowed that some minor increase in transmittance be included in alimited part of the region, provided that the gross transmittance in theregion of 300-400 nm is reduced when viewed as a whole.

[0011] In the ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass, it is preferable that the reduction intransmittance in the wavelength range of 300-400 nm is given as[transmittance after irradiation/transmittance before irradiation]≦0.9when assessed employing transmittance to light having the wavelength of350 nm measured with a 3.5-mm thick sample as an index. More preferably,the value is not more than 0.86.

[0012] By using the ultraviolet-ray absorbing, colorless and transparentsoda-lime-silica glass of the present invention, it has become possibleto further reduce the transmittance to ultraviolet-ray than before,inter alia ultraviolet-ray having wavelengths of 300-350 nm, the lightwhich greatly affects on such contents as refined “sake”.

[0013] In the specification, “light having wavelengths in the far- tonear-ultraviolet region” means ultraviolet-ray having wavelengths in theregion of 200-400 nm.

[0014] In the above-described ultraviolet-ray absorbing, colorless andtransparent soda-lime-silica glass, for reasons mentions later, cerium,as calculated as CeO₂, is contained preferably in a proportion of0.08-0.8% by weight, more preferably in a proportion of 0.10-0.65% byweight, and still more preferably in a proportion of 0.12-0.19% byweight.

[0015] The ultraviolet-ray absorbing, colorless and transparentsoda-lime-silica glass described above may be provided in the form of aglass bottle.

[0016] The ultraviolet-ray absorbing, colorless and transparentsoda-lime-silica glass characterized above may be further characterizedin that its composition includes, in % by weight, SO₃ 0.14-0.37% Ceriumoxide 0.08-0.8%  (calculated as CeO₂) Fe₂O₃ 0.01-0.08% FeO    0-0.008%Manganese oxide   0-0.07% (calculated as MnO) Cobalt oxide    0-0.0005%(calculated as CoO).

[0017] Herein, “cerium oxide” means both of CeO₂ and Ce₂O₃, and its “%by weight” is expressed as a value obtained when all the containedcerium oxide were replaced with CeO₂. Likewise, “manganese oxide” meansboth of MnO and Mn₂O₃, and its “% by weight” is expressed as a valueobtained when all the contained manganese oxide were replaced with MnO.In addition, “cobalt oxide” is also expressed as a value obtained whenall the contained cobalt oxide were replaced with CoO.

[0018] The features of the ultraviolet ray-absorbing, colorless andtransparent soda-lime-silica glass of the present invention, asmentioned above, consists in irradiation of a cerium-containingsoda-lime-silica glass with light having wavelengths in the far- tonear-ultraviolet region, and in that the glass preferably contains, inpredetermined proportions, SO₃, cerium oxide and Fe₂O₃ and FeO, and, asneeded, manganese oxide and/or cobalt oxide. The basic composition ofthe soda-lime-silica glass employed may be within conventional ranges.However, considering needs for high chemical durability, eliminatedpossibility of devitrification and proper easiness of melting, it ispreferable that the ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of the present invention typically comprises, in% by weight: SiO₂ 65-75% Al₂O₃ 0-5% CaO  6-15% MgO 0-4% Na₂O 10-17% K₂O0-4% SO₃ 0.14-0.37% Cerium oxide 0.08-0.8%  (calculated as CeO₂) Fe₂O₃0.01-0.08% FeO    0-0.008% Manganese oxide   0-0.07% (calculated as MnO)Cobalt oxide    0-0.0005% (calculated as CoO).

[0019] The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of the present invention preferably contains0.005-0.07% by weight of manganese oxide as calculated as MnO.

[0020] In addition, to enhance the reliability of the total performanceof the glass of the present invention, it is more preferable that theultraviolet ray-absorbing, colorless and transparent soda-lime-silicaglass of the present invention is characterized in that its compositionincludes, in % by weight, SO₃ 0.15-0.35% Cerium oxide 0.10-0.65%(calculated as CeO₂) Fe₂O₃ 0.015-0.06%  FeO    0-0.006% Manganese oxide0.007-0.06%  (calculated as MnO) Cobalt oxide    0-0.0003% (calculatedas CoO).

[0021] Furthermore, it is more preferable that the ultravioletray-absorbing, colorless and transparent soda-lime-silica glass of thepresent invention comprises, in % by weight, SiO₂ 65-75% Al₂O₃ 0-5% CaO 6-15% MgO 0-4% Na₂O 10-17% K₂O 0-4% SO₃ 0.15-0.35% Cerium oxide0.10-0.65% (calculated as CeO₂) Fe₂O₃ 0.015-0.06%  FeO    0-0.006%Manganese oxide 0.007-0.06%  (calculated as MnO) Cobalt oxide   0-0.0003% (calculated as CoO).

[0022] Furthermore, it is still more preferable that the ultravioletray-absorbing, colorless and transparent soda-lime-silica glass of thepresent invention is characterized in that its composition includes, in% by weight, SO₃ 0.15-0.35% Cerium oxide 0.12-0.19% (calculated as CeO₂)Fe₂O₃ 0.02-0.04% FeO    0-0.004% Manganese oxide 0.007-0.06% (calculated as MnO) Cobalt oxide    0-0.0003% (calculated as CoO).

[0023] On a transmittance curve produced by measuring a 3.5-mm thicksample, the ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of the present invention preferably hastransmittance of not more than 2.5% at the wavelength of 330 nm and, inthe visible region of 420-780 nm, transmittance of not less than 87%without having absorption at any particular wavelength.

[0024] In addition, the ultraviolet ray-absorbing, colorless andtransparent soda-lime-silica glass of the present invention preferablyhas dominant wavelength (λ_(d)) at 565-575 nm.

[0025] The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of the present invention has an excellent abilityto absorb ultraviolet ray, in particular ultraviolet ray havingwavelengths of 300-350 nm. Therefore, when used in the form of glassbottles, it can prevent light-induced coloration, discoloration, fadingin color or deterioration of the flavor of the contents, and is highlyeffective, inter alia, for prevention not only of a yellowing in colorand deterioration of the flavor of refined “sake”, which is sensitive toultraviolet ray at wavelengths around 330 nm, but also of coloration,fading in color or deterioration of the flavor of wines.

BRIEF DESCRIPTION OF DRAWINGS

[0026]FIG. 1 is a graph illustrating the transmittance curves of theglasses of Comparative Example 1 in the wavelength range of 300-400 nm.

[0027]FIG. 2 is a graph illustrating the transmittance curves of theglasses of Example 1 in the wavelength range of 300-400 nm.

[0028]FIG. 3 is a graph illustrating the transmittance curves of theglasses of Example 1 in the wavelength range of 300-780 nm.

BEST MODE FOR CARRYING OUT THE INVENTION

[0029] SiO₂, which is a glass network-former, is generally containedpreferably in a proportion of 65-75% by weight. This is because a SiO₂content below 65% by weight might reduce chemical durability of theglass and, on the other hand, a SiO₂ content over 75% by weight mightrender the glass prone to devitrification. Considering chemicaldurability and proneness to devitrification of the glass, it is morepreferable that the SiO₂ is contained in a proportion of 68-74% byweight.

[0030] Al₂O₃, which is an intermediate oxide of glass, serves to enhancechemical durability of the glass. It is not essential that Al₂O₃ becontained. When it is contained, however, it is generally preferablethat Al₂O₃ content is not more than 5% by weight. This is because anAl₂O₃ content over 5% by weight might render the glass difficult tomelt. Considering chemical durability and ease of melting of the glass,it is more preferable that Al₂O₃ is contained in a proportion of 1-4% byweight.

[0031] CaO, which is a glass network-modifier, serves to enhancechemical durability of the glass as well as to improve its easiness ofmelting. CaO is generally contained preferably in a proportion of 6-15%by weight. This is because a CaO content below 6% by weight might leadto insufficient chemical durability, and a CaO content over 15% byweight, in turn, might render the glass prone to devitrification.Considering chemical durability, proper ease of melting and proneness todevitrification of the glass, CaO is contained more preferably in aproportion of 8-13% by weight.

[0032] MgO, which is a glass network-modifier, serves, like CaO, toenhance chemical durability of the glass as well as to improve ease ofmelting. It is not essential that MgO be contained. When it iscontained, however, it is generally preferable that MgO content is notmore than 4% by weight. This is because a MgO content over 4% by weightmight render the glass prone to devitrification. Considering chemicaldurability, ease of melting and proneness to devitrification of theglass, it is more preferable that MgO is contained in a proportion of0.1-3% by weight.

[0033] Na₂O, which is a glass network-modifier, has an effect to promotemelting of raw materials. Na₂O is generally contained preferably in aproportion of 10-17% by weight. This is because a Na₂O content below 10%by weight renders the glass difficult to melt, and, a Na₂O content over17% by weight might, in turn, reduce the chemical durability of theglass. Considering ease of melting and the chemical durability of theglass, it is more preferable that the Na₂O is contained in a proportionof 11-15% by weight.

[0034] K₂O, which is a glass network-modifier, serves, like Na₂O, topromote melting of raw materials. It is not essential that K₂O becontained. When it is contained, however, it is generally preferablethat K₂O content is not more than 4% by weight. This is because a K₂Ocontent over 4% by weight renders the glass prone to devitrification.Considering ease of melting and proneness to devitrification of theglass, it is more preferable that K₂O is contained in a proportion of0.1-3% by weight.

[0035] SO₃ may be a residual component of the glass resulting from thefining agents that were added to the batch in the form of a combinationof salt cake (sodium sulfate) and carbon. The amounts of salt cake,carbon and other oxidizing and reducing agents that govern the redoxstate of the batch may be determined so that the content of SO₃ willfall within the range of 0.14-0.37% by weight. The lower limit of 0.14%by weight is set because a lower content of SO₃ in the glass wouldrender the glass too reductive, which then would increase the ratio ofFeO to Fe₂O₃ while decreasing the ratio of Mn₂O₃ to MnO, even afterdesired amounts of cerium oxide and manganese oxide were added, thuscausing to give the glass a greenish to bluish tint. The upper limit of0.37% by weight is set because a higher content of SO₃ in the glassmight cause seed in the glass. Considering prevention of pale greenishto pale bluish coloration of the glass and removal of seed, it is morepreferable that the content of SO₃ in the glass is regulated to fallwithin the range of 0.15-0.35% by weight.

[0036] Cerium oxide serves as an absorbent of ultraviolet ray and iscontained in the forms of CeO₂ and Ce₂O₃ in the glass of the presentinvention. Although the mutual proportion between CeO₂ and Ce₂O₃ variesdepending on the content of SO₃ and therefore is not clear, they,collectively, are contained preferably at 0.08-0.8% by weight(calculated as CeO₂). This is because a content of cerium oxide below0.08% by weight might provide a glass with only insufficient effect toabsorb ultraviolet ray even after irradiation with light havingwavelengths in the far- to near-ultraviolet region. The upper limit of0.8% by weight is preferable because the effect of irradiation withlight having wavelengths in the far- to near-ultraviolet region would bemade relatively smaller where cerium oxide is contained over 0.8% byweight, and, moreover, the glass would acquire an fluorescent color whenthe content of cerium oxide is coming close to 1% by weight. Consideringthe ultraviolet ray-absorbing effect of the glass obtained, theefficiency of production process, economical efficiency, and preventionof emergence of fluorescence, it is more preferable that the ceriumoxide is contained in a proportion of 0.10-0.65% by weight (calculatedas CeO₂). Furthermore, if a glass being produced has high specificgravity, then part of the glass melt containing the higher amount ofZrO₂ leaching from bricks of the tank furnace, i.e., the part having thehigher specific gravity and usually stagnating on the bottom of the tankfurnace, is likely to be brought upward and get unevenly mixed in theproduct, thereby creating striae in the glass. In order to ensure thatsuch a defect in appearance caused by the addition of high specificgravity cerium oxide is prevented, as well as considering an ultravioletray-absorbing effect of the glass, recycling efficiency of flint glasswhich is generally used as cullet, and economic efficiency, cerium oxideis more preferably contained in a proportion of 0.12-0.19% by weight(calculated as CeO₂).

[0037] Fe₂O₃, like cerium oxide, has an ultraviolet ray-absorbingeffect. However, Fe₂O₃ can effectively absorb ultraviolet ray around 330nm, which cerium oxide by itself is unable to absorb sufficiently.Ultraviolet ray at this wavelength is most relevant to the deteriorationof the quality of refined “sake”. Fe₂O₃ is contained preferably in aproportion of 0.01-0.08% by weight. This is because a Fe₂O₃ contentbelow 0.01% by weight might provide the above effect onlyinsufficiently, and, on the other hand, a Fe₂O₃ content over 0.08% byweight might make it difficult for Mn³⁺ ion to decolorize yellow-greencoloration caused by Fe³⁺ ion. Considering desirable absorption ofultraviolet ray by the glass, in particular ultraviolet ray around 330nm, and prevention of coloration, it is more preferable that of Fe₂O₃ iscontained in a proportion of 0.015-0.06% by weight, and still morepreferable in a proportion of 0.02-0.04% by weight.

[0038] FeO is a component which is inevitably produced during the glassmelting process from contaminant iron in silica sand in the glass batch,or from iron added as Fe₂O₃ to the batch. FeO is not only an unnecessarycomponent for obtaining the ultraviolet ray-absorbing, colorless andtransparent soda-lime-silica glass of the present invention, but itscontent must be not more than 0.008% by weight. This is because a FeOcontent over 0.008% by weight might give the glass a bluish tint. Inorder to constantly obtain colorless and transparent glass without fail,the content of FeO is more preferably not more than 0.006% by weight,and still more preferably not more than 0.004% by weight.

[0039] Manganese oxide is a component for decolorizing the yellow-greencoloration caused by Fe₂O₃ contained as an ultraviolet ray absorbent.It, however, is not an indispensable component, and is containedpreferably at 0-0.07% by weight in accordance with the dose ofirradiation by light having wavelengths in the far- to near-ultravioletregion, the above described contents of SO₃, cerium oxide, Fe₂O₃ andFeO. Although manganese oxide is present in the glass both as MnO andMn₂O₃, at unknown mutual ratio, it is Mn³⁺ ion that has a decolorizingeffect. The above-described content of manganese oxide is the sum of MnOand Mn₂O₃ (calculated as MnO). A total content of manganese oxide over0.07% by weight might lead to red-purple coloration due to the excessiveamount of Mn³⁺ ion, which cannot be fully decolorized even by means ofcobalt oxide added as mentioned below or, even if it is successfullydecolorized, might reduce the brightness of the glass, thereby impairingits transparent appearance. Though manganese oxide, as mentioned above,is not indispensable depending on either the dose of irradiation oflight having the above-mentioned wavelengths or composition of theglass, it is preferable that manganese oxide is contained in aproportion of not less than 0.005% by weight (calculated as MnO) toincrease the stability of production. Considering decolorizing effectand the stability of production, it is more preferable that manganeseoxide is contained in a proportion of 0.007-0.06% by weight.

[0040] Cobalt oxide has an effect to decolorize red-purple colorationdue to Mn³⁺ ion. Addition of cobalt oxide is not essential. Wheresomewhat excess amount of Mn³⁺ ion is present, cobalt oxide may be addedas needed at or below 0.0005% by weight (calculated as CoO) in order todecolorize the red-purple coloration due to the Mn³⁺ ion. A totalcontent of cobalt oxide over 0.0005% by weight might reduce thebrightness of the glass and impair its transparent appearance.Considering the transparent appearance of the glass, it is morepreferable that the total content of cobalt oxide is not more than0.0003% by weight (calculated as CoO).

[0041] By irradiating a glass having a composition within the abovedescribed ranges with light having wavelengths in the far- tonear-ultraviolet region, it has become possible to obtain an ultravioletray-absorbing, colorless and transparent soda-lime-silica glass which,on a transmittance curve produced by measuring a 3.5-mm thick sample,has transmittance of not more than 2.5% at the wavelength of 330 nm and,in the visible region of 420-780 nm, transmittance of not less than 87%without having absorption at any particular wavelength. Havingtransmittance of not more than 2.5% at the wavelength of 330 nm isparticularly effective in preventing a yellowing in color anddeterioration of the flavor of refined “sake”. More preferably,transmittance at the wavelength of 330 nm is not more than 2%. Forprotection of a variety of contents, transmittance at the wavelength of350 nm is more preferably not more than 30%, ant still more preferablynot more than 25%.

[0042] It is preferable that the dominant wavelength (λ_(d)) of theglass of the present invention is 565-575 nm. This is because this typeof glass, which has no absorption at any particular wavelength in thevisible region, would have a bluish tint when its dominant wavelength(λ_(d)) is below 565 nm, and a reddish tint when it is over 575 nm. Tobe completely colorless, the dominant wavelength (λ_(d)) of the glass ofthe present invention is more preferably 567-573 nm.

[0043] A general method of producing the glass and glass bottles of thepresent invention is as follows. Briefly, to 100 parts by weight ofsilica sand are added 25-36 parts by weight of soda ash, 23-33 parts byweight of limestone, 0.03-0.15 part by weight of carbon (85% by weightof purity), 0.7-2.0 parts by weight of salt cake (sodium sulfate),0.1-1.1 parts by weight of cerium oxide (as CeO₂) and 0-0.08 part byweight of iron oxide (added in the form of Fe₂O₃ when the amount ofcontaminant iron in the silica sand is insufficient), the last two ofwhich, i.e., cerium oxide and iron oxide, serve as ultraviolet rayabsorbents, and 0-0.12 part by weight of manganese oxide (as MnO₂ of 80%by weight of purity) and 0-0.0007 part by weight of cobalt oxide (asCo₃O₄), the last two of which, i.e., manganese oxide and cobalt oxide,serve as decolorizing agents, and thus prepared batch composition ismelted at 1400-1500° C., then adjusted to 1200-1350° C. in a workingend, passed through a feeder and then into a molding machine, where theglass is formed into bottles at a temperature range of 700-1000° C.Formed bottles are introduced into an annealing lehr so that strain isremoved at 500-600° C., cooled over 30 min to 2 hrs to ambienttemperature, and irradiated with the far- to near-ultraviolet ray toprovide the final products.

[0044] Although soda-lime-silica glass usually includes as a componentseveral % by weight of Al₂O₃, additional raw materials such as alumina,aluminium hydroxide and feldspar may be further added to adjust thecomposition if the amount of the contaminant alumina component in thesilica sand is insufficient.

[0045] Where cullet is employed, blending proportions of the batch maybe modified in accordance with the amounts of SO₃, cerium oxide, ironoxide, manganese oxide and cobalt oxide contained in the cullet.

EXAMPLES

[0046] The present invention is described in further detail below withreference to a comparative example and examples. However, it is notintended that the present invention be limited to those examples.

[0047] In the comparative example and the examples, brightness (Y),dominant wavelength (λ_(d)), excitation purity (Pe) were calculated bythe CIE method provided in JIS Z 8701 based on transmittance curvesproduced by measuring 3.5-mm thick, mirror-polished samples on aspectrophotometer [U-3410, manufactured by HITACHI, LTD.] and convertingthe values into those corresponding to 10-mm thick samples.

[0048] Compositional analysis of the glass was made on a X-rayfluorescence analyzer (3070: manufactured by RIGAKU). The ratio of Fe₂O₃to FeO was calculated based on the absorbance measured at the wavelengthof 1000 nm on the spectrophotometer.

Comparative Example

[0049] A batch composition was prepared by weighing and mixing thefollowing components. Kemerton silica sand 100 parts by weight Soda ash27.5 parts by weight Limestone 27.5 parts by weight Salt cake (sodiumsulfate) 1.4 parts by weight Carbon (85% by weight of purity) 0.06 partby weight Se 0.002 part by weight Co₃O₄ 0.00015 part by weight

[0050] The batch composition thus provided was introduced into acontinuous tank furnace having a melting capacity of 150 t/day andmelted at a glass melting temperature of 1450° C. for 38 hours, thenpassed through a feeder at 1270° C., molded and passed along a lineequipped with a conventional annealing lehr to give bottles having acapacity of 300 mL.

[0051] Compositional analysis of this glass by X-ray fluorescencespectrometry (by spectrophotometry with regard to the proportion betweenFe₂O₃ and FeO) gave the following proportions (% by weight) ofcomponents of the composition. SiO₂ 71% Al₂O₃ 2% CaO 11.3% MgO 0.15%Na₂O 12.5% K₂O 1.4% SO₃ 0.225% Fe₂O₃ 0.025% FeO 0.0080% Se 0.00005%Cobalt oxide 0.00012% (calculated as CoO)

[0052] Four of the bottles obtained above were taken at random. One ofthem was set aside as a control glass bottle and the other three wereirradiated with light emitted from an 80 W/cm high-pressure mercury arclamp (HHL-4000/C-FS, OAK SEISAKUSHO KK) for 10, 30 or 60 seconds,respectively. Dose of irradiation of light within the wavelength rangeof 320-390 nm was simultaneously measured with a low-profile ultravioletilluminometer/actinometer (Model UV-351, OAK SEISAKUSHO KK). The dosesof irradiation with ultraviolet ray were 4.8 J/cm², 14.4 J/cm² and 28.8J/cm², respectively.

[0053] 3.5-mm thick samples for measurement were cut out of the controland irradiated glass bottles, mirror-polished and measured to producetransmittance curves on the spectrophotometer. The transmittance curvesthus obtained are shown in FIG. 1 in the wavelength range of 300-400 nm.The control glass bottle had brightness (Y) of 85.8%, dominantwavelength (λ_(d)) of 572.1 nm, and excitation purity (Pe) of 1.01% andthus was colorless and transparent. However, its transmittance to lightat the wavelength of either 350 nm or 330 nm was no less than 84.2% or61.6%, respectively, indicating it hardly provides shielding againstlight at those wavelengths. As to the other bottles, which had the samecomposition as the control bottle and had been irradiated for 10, 30 or60 seconds, the transmittance to ultraviolet ray showed only a slightestdecrease and was still kept at high levels, indicating that theirradiation provided no substantial improvement in shielding effectagainst light at those wavelengths.

Example 1

[0054] A batch composition was prepared by weighing and mixing thefollowing components. Kemerton silica sand 100 parts by weight Soda ash27.5 parts by weight Limestone 27.5 parts by weight Salt cake (sodiumsulfate) 1.4 parts by weight Carbon (85% by weight of purity) 0.06 partby weight CeO₂ 0.12 part by weight MnO₂ (80% by weight of purity) 0.035part by weight Co₃O₄ 0.00015 part by weight

[0055] The batch composition thus provided was introduced into acontinuous tank furnace having a melting capacity of 150 t/day andmelted at a glass melting temperature of 1450° C. for 38 hours, thenpassed through a feeder at 1270° C., molded and passed along a lineequipped with a conventional annealing lehr to give bottles having acapacity of 300 mL.

[0056] Compositional analysis of this glass by X-ray fluorescencespectrometry (by spectrophotometry with regard to the proportion betweenFe₂O₃ and FeO) gave the following proportions (% by weight) ofcomponents of the composition. SiO₂ 71%  Al₂O₃ 2% CaO 11.3% MgO 0.15%Na₂O 12.5% K₂O 1.4% SO₃ 0.258% Cerium oxide 0.09% (calculated as CeO₂)Fe₂O₃ 0.028% FeO 0.0050% Manganese oxide 0.021% (calculated as MnO)Cobalt oxide 0.00012% (calculated as CoO)

[0057] Four of the bottles obtained above were taken at random. As donein Comparative Example, one of them was set aside as a control glassbottle and the other three were irradiated with light emitted from an 80W/cm high-pressure mercury arc lamp (HHL-4000/C-FS, OAK SEISAKUSHO KK)for 10, 30 or 60 seconds, respectively. Dose of irradiation of lightwithin the wavelength range of 320-390 nm was simultaneously measuredwith a low-profile ultraviolet illuminometer/actinometer (Model UV-351,OAK SEISAKUSHO KK). The doses of irradiation with ultraviolet ray were4.8 J/cm², 14.4 J/cm² and 28.8 J/cm², respectively.

[0058] 3.5-mm thick samples for measurement were cut out of the controland irradiated glass bottles, mirror-polished and measured to producetransmittance curves on the spectrophotometer. The results are shown inFIG. 2 (300-400 nm) and FIG. 3 (300-780 nm). The control glass bottle(0-second irradiation) had brightness (Y) of 86.6%, dominant wavelength(λ_(d)) of 566.7 nm, and excitation purity (Pe) of 0.64%. Itstransmittance to light at the wavelengths of either 350 nm or 330 nm was57.2% or 5.5%, respectively (FIG. 2). In addition, in the visible regionof 420-780 nm, its transmittance was not less than 87% without anyapparent rise or fall in absorption at a particular wavelength (FIG. 3).Thus, this control glass bottle of this Example is colorless andtransparent, and has significantly reduced transmittance to ultravioletray compared with the glass bottles of Comparative Example above.Furthermore, the other bottles, which had the same composition as thecontrol bottle and had been irradiated for 10, 30 or 60 seconds,exhibited further reduction in transmittance to ultraviolet ray (FIG. 2and Table 2) as compared with the control bottle. More specifically,while the transmittance of the control glass bottle was 57.2% to lightat the wavelength of 350 nm, those of the bottles irradiated for 10, 30or 60 seconds were further reduced to 44.4%, 32.9% or 31.5%,respectively. Furthermore, the transmittance to light at the wavelengthof 330 nm, which was 5.5% for the control glass bottle, was furtherreduced to 3.5%, 2.3% or 2.1% for the bottles irradiated for 10, 30 or60 seconds, respectively (FIG. 2 and Table 2). On the other hand, theirradiation did not substantially affect on brightness (Y), dominantwavelength (λ_(d)), excitation purity (Pe) or the form of transmittancecurve in the visible region of 420-780 nm (FIG. 3 and Table 2), and thusthe colorless and transparent feature of the bottles remained intact.These results indicate that irradiation of the glass of the compositionof Example 1 with light having wavelengths in the far- to nearultraviolet region provides colorless and transparent glass having stillfurther increased ability of absorbing ultraviolet ray.

Examples 2-6

[0059] According to the blending proportions of batches shown in Table1, glass bottles of Examples 2-6 were produced in the same manner as inComparative Example and Example 1. The bottles were irradiated for 0,10, 30 or 60 seconds in the same matter as described above, and 3.5-mmthick samples were prepared and their color values and transmittancewere measured.

[0060] For each of the the glass, as well as for the glass ofComparative Example and Example 1, the blending proportion of batchesand glass composition are shown collectively in Table 1, and colorvalues and transmittance to light in Table 2, respectively. TABLE 1Compara- tive Exam- Exam- Exam- Exam- Exam- Exam- Example ple 1 ple 2ple 3 ple 4 ple 5 ple 6 Batch blending Kemerton silica 100 100 100 100100 100 100 proportion sand (part(s) by Soda ash 27.5 27.5 27.5 27.527.5 27.5 27.5 weight) Limestone 27.5 27.5 27.5 27.5 27.5 27.5 27.5 Saltcake 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Carbon (85%) 0.06 0.06 0.06 0.06 0.060.06 0.06 CeO₂ 0 0.12 0.23 0.33 0.64 0.81 1.03 MnO₂ (80 %) 0 0.035 0.0890.094 0.059 0.054 0 Se 0.002 0 0 0 0 0 0 Co₃O₄ 1.5 × 1.5 × 1.5 × 1.5 ×1.5 × 1.5 × 0 10⁻⁴ 10⁻⁴ 10⁻⁴ 10⁻⁴ Glass composition SiO₂ 71 71 71 71 7171 71 (% by weight) Al₂O₃ 2 2 2 2 2 2 2 CaO 11.3 11.3 11.3 11.3 11.311.3 11.3 MgO 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Na₂O 12.5 12.5 12.512.5 12.5 12.5 12.5 SO₃ 0.225 0.258 0.266 0.265 0.285 0.286 0.287 Ceriumoxide 0 0.09 0.17 0.25 0.48 0.61 0.77 (calculated as CeO₂) Fe₂O₃ 0.0250.028 0.034 0.035 0.032 0.033 0.032 FeO 0.0080 0.0050 0.0022 0.00140.0007 0.0003 0.0003 Manganese oxide 0 0.021 0.054 0.057 0.036 0.033 0(calculated as MnO) Se 5 × 0 0 0 0 0 0 10⁻⁵ Cobalt oxide 1.2 × 1.2 × 1.2× 1.2 × 1.2× 1.2× 0 (calculated as CoO) 10⁻⁴ 10³¹ ⁴ 10⁻⁴ 10⁻⁴ 10⁻⁴ 10⁻⁴

[0061] TABLE 2 Irradiation Comparative (sec) Example Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Color values Y (%) 0 85.8 86.687.2 87.4 87.0 87.1 88.9 10 85.3 84.3 85.8 83.6 84.7 86.3 87.8 30 84.779.6 84.7 82.6 80.6 85.7 87.4 60 85.1 82.1 83.4 83.7 83.7 84.5 86.7λ_(d) (nm) 0 572.1 566.7 566.4 566.5 572.2 573.8 573.0 10 573.1 569.2570.0 570.5 573.0 572.9 573.0 30 575.2 572.4 573.1 573.6 574.3 572.9573.3 60 575.4 570.5 573.8 574.1 572.3 575.4 573.1 Pe (%) 0 1.01 0.640.61 0.63 0.75 0.92 1.50 10 1.10 0.85 0.82 0.80 0.94 1.07 1.67 30 1.211.04 0.88 0.78 1.32 0.92 1.66 60 1.23 0.69 0.88 0.56 0.93 1.12 1.54Transmittance 0 61.6 5.5 3.8 3.4 3.1 2.7 2.5 (%) (330 nm) 10 59.5 3.52.9 3.0 2.6 1.8 1.7 30 56.3 2.3 2.0 1.9 1.8 1.8 1.6 60 56.9 2.1 1.9 1.81.8 1.8 1.5 Transmittance 0 84.2 57.2 43.4 33.0 14.3 11.0 7.3 (%) (350nm) 10 82.8 44.4 34.0 27.7 12.7 9.4 6.0 30 81.1 32.9 31.3 22.2 10.3 9.15.7 60 81.0 31.5 24.3 21.1 9.9 7.4 4.7 Transmittance 0 ≧87 ≧87 ≧87 ≧87≧87 ≧87 ≧87 (%) 10 ≧87 ≧87 ≧87 ≧87 ≧87 ≧87 ≧87 (420-780 nm) 30 ≧87 ≧87≧87 ≧87 ≧87 ≧87 ≧87 60 ≧87 ≧87 ≧87 ≧87 ≧87 ≧87 ≧87

[0062] From Table 2, it is evident that irradiation with light withwavelengths in the far- and near-ultraviolet region gives colorless andtransparent glass with further reduced transmittance to ultraviolet ray.

INDUSTRIAL APPLICABILITY

[0063] The present invention enables to produce ultravioletray-absorbing, colorless and transparent soda-lime-silica glass andglass bottles made of the glass which, while having high transmittanceto light in the visible region, blocks ultraviolet ray more effectivelythan before. Therefore, the present invention is applicable toproduction of glass bottles which can prevent coloration, discoloration,fading in color or deterioration of the flavor of their contents, interalia, glass bottles which can prevent a yellowing in color of refined“sake” and coloration or fading in color of wines, as well asdeterioration of the flavor of refined “sake” and wines.

1. An ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass wherein the glass is prepared by irradiating acerium containing soda-lime-silica glass with light having wavelengthsin the far- to near-ultraviolet region and thereby reducingtransmittance to light with wavelengths in the region of 300-400 nm. 2.The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of claim 1 wherein the reduction in transmittancein the wavelength range of 300-400 nm is given as [transmittance afterirradiation/transmittance before irradiation]≦0.9 when assessedemploying transmittance to light having the wavelength of 350 nmmeasured with a 3.5-mm thick sample as an index.
 3. The ultravioletray-absorbing, colorless and transparent soda-lime-silica glass of claim1 or 2 wherein the glass comprises cerium in a proportion of 0.08-0.8%by weight as calculated as CeO₂.
 4. The ultraviolet ray-absorbing,colorless and transparent soda-lime-silica glass of claim 1 or 2 whereinthe glass is characterized in that the composition of the glassincludes, in % by weight, SO₃ 0.14-0.37% Cerium oxide 0.08-0.8% (calculated as CeO₂) Fe₂O₃ 0.01-0.08% FeO    0-0.008% Manganese oxide  0-0.07% (calculated as MnO), and Cobalt oxide    0-0.0005% (calculatedas CoO).


5. The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of claim 1 or 2 wherein the glass comprising, in% by weight, SiO₂ 65-75% Al₂O₃ 0-5% CaO  6-15% MgO 0-4% Na₂O 10-17% K₂O0-4% SO₃ 0.14-0.37% Cerium oxide 0.08-0.8%  (calculated as CeO₂) Fe₂O₃0.01-0.08% FeO    0-0.008% Manganese oxide   0-0.07% (calculated as MnO)Cobalt oxide    0-0.0005% (calculated as CoO).


6. The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of claim 4 or 5 wherein the glass containing0.005-0.07% by weight of manganese oxide as calculated as MnO.
 7. Theultraviolet ray-absorbing, colorless and transparent soda-lime-silicaglass of claim 1 or 2 wherein the glass is characterized in that thecomposition of the glass includes, in % by weight, SO₃ 0.15-0.35% Ceriumoxide 0.10-0.65% (calculated as CeO₂) Fe₂O₃ 0.015-0.06%  FeO    0-0.006%Manganese oxide 0.007-0.06%  (calculated as MnO), and Cobalt oxide   0-0.0003% (calculated as CoO).


8. The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of claim 1 or 2 wherein the glass ischaracterized in that the composition of the glass includes, in % byweight, SO₃ 0.15-0.35% Cerium oxide 0.12-0.19% (calculated as CeO₂)Fe₂O₃ 0.02-0.04% FeO    0-0.004% Manganese oxide 0.007-0.06% (calculated as MnO), and Cobalt oxide    0-0.0003% (calculated as CoO).


9. The ultraviolet ray-absorbing, colorless and transparentsoda-lime-silica glass of one of claims 1 to 8 wherein the glass has, ona transmittance curve produced by measuring a 3.5-mm thick sample,transmittance of not more than 2.5% at the wavelength of 330 nm and has,in the visible region of 420-780 nm, transmittance of not less than 87%without having absorption at any particular wavelength.
 10. Theultraviolet ray-absorbing, colorless and transparent soda-lime-silicaglass of one of claims 1 to 9 wherein the glass has dominant wavelength(λ_(d)) at 565-575 nm.
 11. The ultraviolet ray-absorbing, colorless andtransparent soda-lime-silica glass of one of claims 1 to 10 wherein theglass is formed into a glass bottle.